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Life Science Notes Chapter 3
3.1 Chemistry of Life
Matter is anything that has mass and takes
up space.
Energy- is anything that brings about
change.
Energy can hold matter together or break it
apart.
Atom are small particles that makes up
matter.
At the center of an atom is a nucleus that
contains protons and neutrons
Protons have a positive charge, and
neutrons have no charge.
Outside of the nucleus are electrons which
have a negative charge.
Electrons are the part of the atom that are
involved in chemical reactions.
An atom is mostly empty space. Energy
holds the parts of an atom together.
When something is made up of only one
kind of atom it is called an element
An element can’t be broken down to a
simpler form by chemical reactions.
Scientists have given each element a one or
two letter symbol
All elements are arranged in a chart known
as the periodic table of elements.
Compounds are made up of two or more
elements in exact proportion.
There are two types of compoundsmolecular and ionic.
The smallest part of a molecular compound
is a molecule.
A molecule is a group of atoms held
together by the energy of chemical bonds.
When chemical reactions occur, chemical
bonds break, atoms are rearranged, and new
molecules form. 6CO + 6H O + energy =
C H O6 + 6O
2
6
12
2
2
Molecular compounds form when different
atoms share their outer most electrons.
Atoms also combine because they’ve
become positively or negatively charged.
Atoms are usually neutral- they have no
overall electric charge.
When an atom loses an electron it becomes
positively charged.
When an atom gains an electron it becomes
negatively charged.
Electrically charged atoms are called ions
Ions of opposite charges attract one another
to form electrically neutral compounds
called ionic compounds.
Table salt is made of sodium and chlorine
ions.
Potassium and sodium ions help nerve cells
send messages.
Calcium ions make muscles contract.
A mixture is a combination of substances in
which individual substances retain their
own properties.
Mixtures can be solids, liquids, gases or any
combination of them.
Most reactions in living organisms take
place in mixtures called solutions.
In a solution 2 or more substances are mixed
evenly.
A suspension is formed when a liquid or a
gas has another substance evenly spread
throughout it.
Unlike solutions, the substances in a
suspension eventually sink to the bottom.
Rocks and other nonliving things contain
inorganic compounds.
Organic compounds always contain carbon
and hydrogen and usually are associated
with living things.
Four groups of organic molecules make up
all living things- Carbohydrates, lipids,
proteins and nucleic acids.
Carbohydrates are organic molecules that
supply energy for cell processes.
Sugar and starches are carbohydrates that
cells use for energy.
Some carbs are also important parts of cell
structures like parts of the cell membrane.
Lipids do not mix with water.
Lipids such as fats and oils store and release
even larger amounts of energy than
carbohydrates do.
Proteins are made up of smaller molecules
called amino acids.
Proteins are the building blocks of many
structures in organisms.
Certain proteins called enzymes regulate all
chemical reactions in cells.
Large organic molecules that store
important coded information in cells are
called nucleic acids.
One nucleic acid, deoxyribonucleic acid, or
DNA-genetic material- is found in all cells
at some point in their lives.
Another nucleic acid, ribonucleic acid or
RNA is needed to make enzymes and other
proteins.
Most inorganic compounds are made from
elements other than carbon.
Inorganic compounds are the source for
many elements needed by living things.
Inorganic compounds can contain the
elements nitrogen, phosphorus, and sulfur.
One of the most important inorganic
compounds for living things is water.
Living things are made of more than 50%
water and depend on water to survive.
Seeds and spores of plants, fungi and
bacteria need water if they are to grow and
reproduce.
All chemical reactions take place in water
solutions, and organisms use water to move
materials through their bodies.
The atoms of a water molecule are arranged
in a way that the molecule has areas with
different charges.
Water molecules are like magnet.
This attraction between water molecules
makes the surface like a film. This is the
reason that bugs can walk on it.
Because water molecules are so strongly
attracted to each other, the temperature of
water changes slowly.
The large % of water in living things acts
like an insulator.
The water in a cell helps keep its
temperature constant, which allows life
sustaining chemical reactions to take place.
When water freezes ice crystals form.
In the crystals, each water molecule is
spaced at a certain distance from all others.
Because this space is greater in frozen water
than in liquid water, ice floats on water.
Bodies of water freeze from the top down.
The floating ice provides insulation and
allows living things to survive.
3
.1 Moving cellular Materials
Cells take in food, oxygen and other
substances from their environment.
They also release waste materials.
A cell has a membrane around it that works
like a window screen.
A cells membrane is selectively permeable
It allows some things to enter and leave the
cell while keeping other things outside or
inside the cell.
The movement of substances through the
cell membrane without the input of energy is
called passive transport.
There are 3 kinds of passive transport.
The movement of molecules from areas
where there are many molecules to areas
where there are few molecules is called
diffusion.
Molecules will continue to move until the
areas are equal. When this occurs
equilibrium is reached and diffusion stops.
Water molecules move by diffusion into and
out of cells. The diffusion of water through
the cell membrane is called osmosis.
Some substances are too large to pass with
diffusion so they can only enter with the
help of molecules. Usually these molecules
are transport proteins. This process still
doesn’t require energy and it is called
facilitated diffusion.
When input of energy is required to move
materials through the cell membrane, active
transport takes place.
The process of taking substances into a cell
by surrounding it with the cell membrane is
called endocytosis. Some one-celled
organisms take in food this way.
Exocytosis occurs in the opposite way as
endocytosis. A vesicles membrane fuses
with the cell membrane and the vesicles
contents are released.
.1 Energy For Life
The total of all chemical reactions in an
organism is called metabolism.
The chemical reactions of metabolism need
enzymes.
Enzymes in cells cause change but the
enzyme does not change. It can be used
again. They can cause molecules to join or
break apart. Without the right enzyme a
chemical reaction cannot take place. Each
chemical reaction in a cell requires a
specific enzyme.
Organisms that make their own food, such
as plants are called producers.
Organisms that cannot make their own food
are called consumers.
During photosynthesis producers use light
energy to make sugars, which can be used as
food.
The captured light energy is used to drive
the chemical reactions during which the raw
materials carbon dioxide and water are used
to produce sugar and oxygen.
For plants, raw materials come from air and
soil.
Some of the captured light energy is stored
in the chemical bonds that hold sugar
molecules together.
Plants make more sugar during
photosynthesis than they need for survival.
Excess sugar is changed and stored as
starches or used to make other
carbohydrates.
Plants use carbohydrates as food for growth,
maintenance and reproduction.
Consumers take in food by eating producers
or other consumers.
Some of the energy from the food you eat is
used to make you move.
Some of it becomes thermal energy, which
keeps you warm.
Most cells need oxygen to break down food.
During cellular respiration chemical
reactions occur that break down food into
simpler substances and release their stored
energy.
Enzymes are needed just like in
photosynthesis.
The type of food most easily broken down
by cells is carbohydrates.
Respiration of carbohydrates begins in the
cytoplasm of the cell.
The carbohydrates are usually broken down
into simpler molecules.
Glucose is broken down into two simpler
molecules.
As glucose molecules are broken down,
energy is released.
The two simpler molecules are broken down
again. This breakdown occurs in the
mitochondria of the cells of plants, animals,
fungi and many other organisms.
This process uses oxygen releases much
more energy and produces carbon dioxide
and water as wastes.
When you exhale you breathe out carbon
dioxide and some of the water.
Respiration occurs in the cells of many
living things.
When cells do not have enough oxygen for
respiration they use a process called
fermentation to release some of the energy
stored in glucose molecules.
Like respiration, fermentation begins in the
cytoplasm.
Again as the glucose molecules are broken
down, energy is released.
But the simple molecules from the
breakdown of glucose do not move into the
mitochondria.
Instead, more chemical reactions occur in
the cytoplasm.
The reactions produce some energy and
produce wastes.
Depending on the type of cell, the wastes
may be lactic acid
alcohol and carbon dioxide.
The presence of lactic acid is why your
muscles might feel stiff and sore after you
exercise.
During photosynthesis and respiration, what
is produced in one is used in the other.
Photosynthesis produces sugars and oxygen,
and respiration uses these products.
The carbon dioxide and water produced
during respiration are used during
photosynthesis.